As far as i know you can't do this with windows onboard tools. You can try using the Software Router/Switch/Bridge from Vmware or Virtualbox, don't know if this will work as expected but there you can give a virtual PC an own Macadress but bridge it to the Networkcard of the Host so maybe there is a way to use this Mechanism. Maybe also the aproach mentioned here forum.openwrt.org/viewtopic.php?id=31007 will help you.
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konquiMar 16 '14 at 10:19

There is a way to do it when configuring VMs in Hyper-V. Basically, the adapter becomes a virtual switch. Each VM gets its own virtual NIC with its own MAC address. To the outside world, the one physical adapter looks/behaves like an array of adapters, each with its own MAC and IP address. When using Hyper-V this is all done using the Hyper-V Manager (or equivalent). I don't know if/how it can be done through ipconfig to achieve the result you are seeking.
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ZenilogixSep 1 '14 at 2:31